This application is a 35 USC 371 National Stage of PCT/DK99/00214 filed Apr. 16, 1999.
The invention relates to an apparatus for sterilizing a member including equipment for surgery or medical examination, such as dental handpieces, endoscopes, or catheters. Furthermore, the invention relates to methods for sterilizing a member.
After surgery or medical examination of a patient, the equipment used has to be sterilized so that the equipment does not transport any bacteria or virus from the patient to the next patient. Typically, the equipment is sterilized in an autoclave. The autoclave sterilizes outer surfaces of the equipment by subjecting the equipment to an atmosphere of saturated heated aqueous vapor at 120xc2x0 C. and at a pressure of 2 atmospheres for 20-30 minutes, or for even longer time periods.
It is a disadvantage of an autoclave that repeated sterilization in the autoclave wears and tears on autoclaved members as most materials used for manufacture of such members show a low resistance to aqueous vapor at high temperatures and pressures. For example, members comprising optical components or components made of rubber or silicon can not be sterilized in an autoclave due to those components having a low resistance to the environment in an autoclave.
It is another disadvantage of sterilization in an autoclave that it often takes several minutes or up to one hour to obtain sterilization. Further, heating members in the autoclave also requires time for cooling the member to room temperature. Typically, surgeons or dentists do not have time to wait for their instruments to be autoclaved, and this means that such instruments are not autoclaved as often as may be desired.
DE 29 04 391 discloses an apparatus for sterilizing, such as dental or medical equipment, by use of a source of ultraviolet light and ozone. Members to be sterilized are positioned on shelves in a box. Ozone circulates within the box by convection generated by a heating arrangement.
DE 34 40 078 discloses an apparatus for sterilizing dental equipment. The equipment is sterilized by ultraviolet light provided in a sterilization housing. The equipment is positioned on a dental tray, the tray being vertically movable, so that the tray with the equipment may be moved vertically up and into the sterilization housing wherein an ultraviolet lamp is positioned.
It is an object of the present invention to provide an apparatus that is capable of sterilizing members, such as dental or medical instruments, in a short time, such as shorter than 5 minutes. Thus, users of the members may sterilize members frequently, for example after each individual treatment of a patient.
It is a further object of the present invention to provide a sterilization process that results in a shorter sterilization time than the known processes such as the autoclave sterilization.
It is another object of the present invention to provide an apparatus that is capable of sterilizing members that do not cause wear and tear on members to be sterilized.
These objects are achieved by an apparatus for sterilizing a member which, in a first aspect of the present invention, comprises a housing defining an enclosure therein for receiving and holding the member, and a first source of ultraviolet light for illuminating the member with ultraviolet light and which is positioned in the enclosure.
According to the invention, the sterilization of a member is performed by positioning the member in the enclosure defined by the housing. In the enclosure, the first source of ultraviolet light is positioned for illumination of the member. Wall parts of the enclosure may be shaped to increase the intensity of ultraviolet light illuminating the member to be sterilized. The wall parts may have surfaces that reflect ultraviolet light, whereby the ultraviolet light illuminates the entire surface area of the member.
Micro organisms are killed by ultraviolet light since such light breaks DNA strings in the organism. The killing efficiency of the ultraviolet light depends on its wavelength. It has been found that, preferably, the wavelength of the ultraviolet light ranges from 249 to 259 nm, preferably from 250 to 258 nm or from 251 to 257 nm, or more preferably from 252 to 256 nm or from 253 to 255 nm, and most preferably approximately 253.7 nm.
In a preferred embodiment of the invention, the apparatus may further comprise an ozone source for generating ozone to be brought into contact with surfaces. For example, ozone may contact internal surfaces of a member that are not illuminated by the ultraviolet light, for sterilization of the contacted surfaces.
The apparatus may further comprise a pump connected to the ozone source for generation of a forced ozone flow within the enclosure, and a holding component positioned in the enclosure and adapted to receive and hold the member. Preferably, the holding component is connected to the pump so that the ozone flow passes over internal surfaces of the member. Thus, internal surfaces of the member that are not illuminated by the ultraviolet light for sterilization of the contacted surfaces are sterilized by ozone. The ozone has a chemical structure that is toxic and kills micro organisms within a short time.
The pump forces a flow of atmospheric air or oxygen into the ozone generating source, and after the air or oxygen has passed the ozone generator, the ozone is blown into the enclosure and into internal conduits of the member. The pump may blow atmospheric air or oxygen into the ozone generator or may draw air with ozone from the ozone generator. However, in a preferred embodiment, the pump blows atmospheric air or oxygen into the ozone generator so that ozone does not enter the pump.
When sterilizing a member in the enclosure, the member may be positioned in the enclosure on shelves, hanging on wires, etc. However, in a preferred embodiment of the present invention, the apparatus further comprises holding component positioned in the enclosure and adapted to receive and hold the member. The holding component may be a plate having apertures for receiving the members to be sterilized. In a preferred embodiment, the apertures may be positioned in a pipe stub that fits the member to be sterilized. The member is positioned over the pipe stub. The ozone flows through the stub and into internal conduits of the member. The connection between the ozone generator and the holding component may be provided by plastic tubes, rubber tubes, or steel tubes or any other type of tubes that are able to transport ozone.
The generation of ozone in the ozone source may be provided either by sparking in atmospheric air or by illuminating atmospheric air or oxygen with ultraviolet light. In a preferred embodiment, the apparatus comprises an ozone generator that includes its own source of ultraviolet light for generating ozone. By illumination of oxygen with ultraviolet light, oxygen is transformed into ozone. When passing a flow of atmospheric air or oxygen through the generator, the atmospheric air or oxygen is illuminated with ultraviolet light having a preferred wavelength that is particularly effective in transforming oxygen to ozone. The ozone may then be forced into the enclosure and into the internal parts of the member to be sterilized via the above-mentioned stubs.
For effective transformation of oxygen into ozone, the wavelength of the ultraviolet light preferably ranges from 179 to 189 nm, preferably from 180 to 188 nm, such as from 181 to 187 nm, more preferred from 182 to 186 nm, and even more preferred from 183 to 185 nm. It is presently most preferred that the wavelength is approximately 183.7 nm.
The apparatus may further comprise a heating device for heating the forced flow of ozone, so as to increase the activity of the ozone molecules and thereby provide an improved sterilization of surfaces (such as internal surfaces) of the member to be sterilized. The temperature of the heated flow ranges preferably from 40 to 80xc2x0 C., more preferred from 50 to 70xc2x0 C., and is most preferred approximately 60xc2x0 C.
It is an important advantage of the present invention that the number of living micro organisms in a-member after sterilization in the apparatus is reduced by at least a factor of 106. The determined reduction factor is in conformance with the international specification (Ph. Eur. 3rd. Ed. (1997) 2.6.1, Sterility) concerning sterilization of equipment. The apparatus is tested by sterilizing a member having been deliberately contaminated with the bacteria xe2x80x9cBacillus subtilis var. nigerxe2x80x9d. 
Furthermore, the apparatus may be able to disinfect a member, so that the number of micro organisms in the member after the disinfection is less than 105 living micro organisms, less than 104 living micro organisms, less than 103 living micro organisms, less than 102 living micro organisms, or most preferably less than 10 living micro organisms.
As mentioned above, the member being sterilized may be positioned on a holding component which may be positioned in the enclosure. To avoid any contacts after sterilization between the member to be sterilized and the surrounding atmosphere or the human operator, the member may be covered by a substantially sealed bag.
The bag for covering the member may be a closed bag with only one opening in the bottom, so that the bag may be pulled over the member from above before the member is introduced to the enclosure and positioned on the holding component. After sterilization, the member and the bag may be removed from the holding component. The opening in the bottom of the bag is provided with a closing device that will close the bag when it is removed from the holding component. The closing device may be any kind of spring loaded mechanism (like the closing device known from small wallets) which may be made of steel, plastic or rubber, pasty-like sealing, etc. The bag may be made of any kind of material that is penetrable by ultraviolet light.
Furthermore, the apparatus comprises an ozone neutralizing device for removing ozone so that ozone is prevented from leaving the apparatus and entering the surroundings of the apparatus. The ozone neutralizing device may comprise an active carbon filter facilitating transformation of ozone into oxygen. Ozone is not a stable molecule and interaction with the carbon atoms in the carbon filter causes ozone to be transformed into oxygen. The carbon filter may be connected to a fan that forces, e.g. draws, the ozone through the carbon filter.
The housing of the apparatus may be painted on its inner surfaces with an ozone neutralizing paint for further prevention of ozone leaving the enclosure and entering the surrounding area of the apparatus.
The sterilization process performed by the apparatus may be controlled manually or by a processor.
In a preferred embodiment, the apparatus further comprises a processor for controlling operation of the apparatus. The processor is adapted to control the first and second source of ultraviolet light and the pump, and is adapted to control the sterilization process. The processor may be adapted to perform different sterilization processes, each process being characterized by specific parameters, such as duration of illumination by the first ultraviolet light, duration of ozone treatment, etc, and is adapted to sterilize specific types of members.
According to a preferred embodiment of the invention, the processor is adapted to control the apparatus so that the first ultraviolet light source is turned on for approximately 30 seconds, the first ultraviolet light source is turned off, the ozone source is turned on for 30 seconds, and the ozone source is turned off, and ozone within the enclosure is transformed into oxygen to prevent emission of ozone to the surroundings of the apparatus.
It is an important advantage of the apparatus according to the present invention that sterilization of a member is provided within a short time, such as 3 min. Furthermore, the member is subjected to standard pressure and temperature (approximately 1 bar and 20xc2x0 C.) during sterilization minimizing wear and tear of the member.
After completion of a sterilization cycle in the apparatus, ozone in the apparatus is eliminated before access to the enclosure by an operator of the apparatus is allowed. Ozone may be eliminated by transforming ozone into oxygen by recirculating air within the enclosure through the carbon filter, or by illuminating the enclosure by ultraviolet light having a wavelength causing transformation of ozone into oxygen, for example, by illumination by the first source of ultraviolet light.
A second aspect of the present invention relates to an apparatus for sterilizing a member. This apparatus comprises a source of ultraviolet light, a fibre optic probe, interface device at a first end of the fibre optic probe for enabling the fibre optic probe to receive the ultraviolet light such that the ultraviolet light is able to be transmitted along the fibre optic probe, and a cleaning head at a second end portion of the fibre optic probes.
The fibre optic probe and the cleaning head are adapted to sterilize the inside of the equipment.
The apparatus may be used for sterilizing any suitable and appropriate type of members. The apparatus can be used to sterilize parts of a member that are not easily accessible and that may not satisfactorily be cleaned by, for example, an autoclave. Usually, the cleaning head will have a cross sectional size which is substantially the same as the cross sectional size of the fibre optic probe. Generally, the cleaning head should be kept as narrow as possible, so that it is able to be inserted into small openings in the member to be cleaned.
In a preferred embodiment, the cleaning head includes a reflecting device for reflecting the ultraviolet light from the cleaning head. The reflecting device is able to increase the amount of ultraviolet light received in the inner parts being cleaned, and this may increase the speed of sterilization of the member that is sterilized in the apparatus according to this aspect of the present invention.
It the cleaning head includes the reflecting device, the apparatus may be one in which the fibre optic probe has an outer covering (in which the outer covering is removed at the cleaning head), and in which the reflecting device is in direct contact with each optical fibre in the fibre optic probe.
The reflecting device is preferably a plurality of small mirrors. Other types of reflecting device may be employed, so that the reflecting device can also be a single one-way mirror coating which is able to transmit the ultraviolet light and then reflect back the transmitted ultraviolet light. If the reflecting device comprises the plurality of small mirrors, then the mirrors are preferably made of polished steel. Other materials may, however, be employed.
Preferably, the fibre optic probe has only one optical fibre. If desired, however, the fibre optic probe may have more than one optical fibre, such as two, three, four or even five optical fibres.
The interface device may have an inverted T-shape. Other types of interface devices may however be employed.
The apparatus according to this second aspect of the invention may be in the form of a hand held instrument for effecting the sterilization of the member to be sterilized.
Preferably, the apparatus according to the second aspect of the invention may form part of a larger apparatus for also cleaning the outside of the member to be sterilized, such as the apparatus according to the first aspect of the invention. In this case, the apparatus may include a housing for receiving the member to be sterilized and a source of ultraviolet light for cleaning the outside of the member. The housing could be the one which is described in accordance with the first aspect of the invention or it could be any other housing.
The source of ultraviolet light for cleaning the outside of the member may be the source of ultraviolet light for the fibre optic probe, or may be a different source of ultraviolet light. Furthermore, the housing may comprise a holding component for holding the member to be sterilized.
The holding component may be a stand having apertures for receiving the member to be sterilized. Other types of holding components may be employed, such as the holding component in the first aspect of the present invention.
Furthermore, the apparatus according to the second aspect may comprise a source of ozone. The source of ozone may be in the form of a lamp which produces ozone, or the ozone could be generated by sparking in air. The lamp may be an ultraviolet lamp, but one which additionally produces ozone.
The first and second aspect of the present invention may be combined, so that the fibre optic probe is formed as an apparatus according to the first aspect of the invention. A combination provides an apparatus for sterilizing members, and which apparatus comprises all of the above-mentioned sterilizing components in one single apparatus, so that the apparatus comprises a housing which defines an enclosure, one or more ultraviolet light sources, one or more ozone generating sources such as ultraviolet light sources or sparking in air, one or more fibre optic probes, one or more pumps for generating a forced ozone flow within the enclosure and a ventilating grating comprising a fan and an active carbon filter. The ultraviolet light sources for illuminating the outer surfaces of the member and for the fibre optic probe may emit 25 light with a wavelength that ranges from 249 to 259 nm, and the ozone generating sources may emit ultraviolet light with a wavelength that ranges from 179 to 189 nm.
According to a third aspect of the invention, a method of sterilizing a member includes positioning a member in a housing defining an enclosure therein for receiving and holding the member, and turning on a first source of ultraviolet light which is positioned in the enclosure for illuminating the member with ultraviolet light for a first predetermined time interval.
The method of sterilizing a member may be carried out with different first predetermined time intervals, which depend on, for example, the size of the outer surface area and the type of contamination of the member to be sterilized. The first predetermined time interval may range from 10 to 60 seconds, preferably from 20 to 50 seconds, more preferred from 25 to 40 seconds, or even more preferred be approximately equal to 30 seconds.
The method may further comprise turning on, for a second predetermined time interval, a second source of ultraviolet light for generating ozone, and turning on a pump which is connected to the ozone source for generation of a forced ozone flow within the enclosure.
The method of sterilizing a member may be carried out with different first and second predetermined time intervals, which depend on, for example, the size of the outer and inner surface areas and the type of contamination of the member to be sterilized. The second predetermined time interval may range from 10 to 60 seconds, preferably from 20 to 50 seconds, more preferred from 25 to 40 seconds, or even more preferred be approximately equal to 30 seconds.
The steps in the method of sterilizing a member may be performed in another sequence other than the one disclosed above, and may comprise other values of the first and second predetermined time intervals. For example, the turning on of the first and second light source may be performed sequentially in any order or simultaneously, and the time intervals may be adjustable.
According to a fourth aspect of the present invention, a method of sterilizing a member is provided, comprising positioning a member in a housing defining an enclosure therein for receiving and holding the member, and turning on a first source of ultraviolet light, which is positioned in the enclosure for illuminating the member and interface device for a fibre optic probe with ultraviolet light.
The fibre optic probe is connected to the interface device at a first end of the fibre optic probe for enabling the fibre optic probe to receive the ultraviolet light such that the ultraviolet light is able to be transmitted along the fibre optic probes.
The fibre optic probe and a cleaning head are introduced into the internal parts of the member, and the cleaning head is positioned at a second end portion of the fibre optic probe.
Both the apparatuses and the methods described above provide an improved sterilization of a member, because the member is saved from wear and tear caused by a short sterilization time and a low pressure and temperature (room temperature).